Re: IEEE-754 Float to int

Re: IEEE-754 Float to int

[Lucas Tanure]

Hi,

My hardware gives me the board temperature as a float 32bits.
So, at some point my hardware gives me a 32bit IEEE-754 float, like this :

regmap_read(device->regmap, ADDR0, &temp);
value = temp << 16;
regmap_read(device->regmap, ADDR1, &temp);
value |= temp;

So, value has a 32bit float now, and I would like to print over hwmon
sysfs API. Like :

temp
Current temperature as reported by thermal zone (sensor).
Unit: millidegree Celsius
RO, Required


Read 26.92387 --> Read 26923 at /sys/class/hwmon/hwmon0/temp0_input
Simple, no float operations.

How I can do it ?

Thanks!

--
Lucas Tanure

Re: IEEE-754 Float to int

[Guenter Roeck]

On Tue, Nov 22, 2016 at 05:10:54PM +0000, Lucas Tanure wrote:
> Hi,
> 
> My hardware gives me the board temperature as a float 32bits.
> So, at some point my hardware gives me a 32bit IEEE-754 float, like this :
> 
> regmap_read(device->regmap, ADDR0, &temp);
> value = temp << 16;
> regmap_read(device->regmap, ADDR1, &temp);
> value |= temp;
> 
> So, value has a 32bit float now, and I would like to print over hwmon
> sysfs API. Like :
> 
> temp
> Current temperature as reported by thermal zone (sensor).
> Unit: millidegree Celsius
> RO, Required
> 
> 
> Read 26.92387 --> Read 26923 at /sys/class/hwmon/hwmon0/temp0_input
> Simple, no float operations.
> 
> How I can do it ?
> 
Only idea I have is to write a conversion function.
Note that the attribute name should be temp1_input.

Guenter

IEEE-754 Float to int

[Lucas Tanure]

Hi,

At some point my hardware gives me a 32bit IEEE-754 float, like this :

regmap_read(device->regmap, ADDR0, &temp);

value = temp << 16;

regmap_read(device->regmap, ADDR1, &temp);

value |= temp;

So, value has a 32bit float now, and I would like to print just the integer
part, like :
Read 26.92387 --> Print 26.
Simple, no float operations.

How I can do it ?

Thank!

-- 
Tanure
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IEEE-754 Float to int

[Anupam Kapoor]

On Tue, Nov 22, 2016 at 9:35 PM, Lucas Tanure <tanure@linux.com> wrote:

> So, value has a 32bit float now, and I would like to print just the
> integer part, like :
> Read 26.92387 --> Print 26.
>

?how about just typecasting to int ? so :

    int x = (int)(some-float-value)

that should be it right ??


?--
kind regards
anupam?


In the beginning was the lambda, and the lambda was with Emacs, and Emacs
was the lambda.
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IEEE-754 Float to int

[Lucas Tanure]

On Tue, Nov 22, 2016 at 4:19 PM, Anupam Kapoor <anupam.kapoor@gmail.com>
wrote:

>
> On Tue, Nov 22, 2016 at 9:35 PM, Lucas Tanure <tanure@linux.com> wrote:
>
>> So, value has a 32bit float now, and I would like to print just the
>> integer part, like :
>> Read 26.92387 --> Print 26.
>>
>
> ?how about just typecasting to int ? so :
>
>     int x = (int)(some-float-value)
>
But this "some-float-value" must be declared as float ? Can I do that ?

>
> that should be it right ??
>
>
> ?--
> kind regards
> anupam?
>
>
> In the beginning was the lambda, and the lambda was with Emacs, and Emacs
> was the lambda.
>



-- 
Lucas Tanure
Embedded Developer
+55 19 988176559
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IEEE-754 Float to int

[Anupam Kapoor]

On Tue, Nov 22, 2016 at 9:51 PM, Lucas Tanure <tanure@linux.com> wrote:

> But this "some-float-value" must be declared as float ? Can I do that ?
>

?in your example, isn't 'value' a float type? already ?

?--
kind regards
anupam?


In the beginning was the lambda, and the lambda was with Emacs, and Emacs
was the lambda.
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IEEE-754 Float to int

[Lucas Tanure]

No. Is a unsigned int. I'm trying to avoid floats in the kernel.

On Tue, Nov 22, 2016 at 4:28 PM, Anupam Kapoor <anupam.kapoor@gmail.com>
wrote:

>
> On Tue, Nov 22, 2016 at 9:51 PM, Lucas Tanure <tanure@linux.com> wrote:
>
>> But this "some-float-value" must be declared as float ? Can I do that ?
>>
>
> ?in your example, isn't 'value' a float type? already ?
>
> ?--
> kind regards
> anupam?
>
>
> In the beginning was the lambda, and the lambda was with Emacs, and Emacs
> was the lambda.
>



-- 
Lucas Tanure
Embedded Developer
+55 19 988176559
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IEEE-754 Float to int

[Greg KH]

On Tue, Nov 22, 2016 at 04:05:18PM +0000, Lucas Tanure wrote:
> Hi,?
> 
> At some point my hardware gives me a 32bit?IEEE-754 float, like this :
> 
> 
> regmap_read(device->regmap, ADDR0, &temp);
> 
> value = temp << 16;
> 
> regmap_read(device->regmap,?ADDR1, &temp);
> 
> value |= temp;
> 
> 
> So, value has a 32bit float now, and I would like to print just the integer
> part, like :
> Read 26.92387 --> Print 26.?
> Simple, no float operations.?
> 
> How I can do it ?

Just print the upper 16 bits shifted right by 16 bits.

But why would you want to print the value anyway?  Who would use it?

thanks,

greg k-h

IEEE-754 Float to int

[Lucas Tanure]

On Tue, Nov 22, 2016 at 4:39 PM, Greg KH <greg@kroah.com> wrote:

> On Tue, Nov 22, 2016 at 04:05:18PM +0000, Lucas Tanure wrote:
> > Hi,
> >
> > At some point my hardware gives me a 32bit IEEE-754 float, like this :
> >
> >
> > regmap_read(device->regmap, ADDR0, &temp);
> >
> > value = temp << 16;
> >
> > regmap_read(device->regmap, ADDR1, &temp);
> >
> > value |= temp;
> >
> >
> > So, value has a 32bit float now, and I would like to print just the
> integer
> > part, like :
> > Read 26.92387 --> Print 26.
> > Simple, no float operations.
> >
> > How I can do it ?
>
> Just print the upper 16 bits shifted right by 16 bits.


> But why would you want to print the value anyway?  Who would use it?
>
My hardware gives me the board temperature as a float 32bits.
And the hwmon sysfs api asks me to return the temperature as millidegree
Celsius.

To follow the hwmon sysfs api rules
<https://www.kernel.org/doc/Documentation/thermal/sysfs-api.txt>, I need to
get my float, multiply by 1000 and print the integer part.
There is a better way to do that ?


> thanks,
>
> greg k-h
>

Thanks

-- 
Lucas Tanure
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IEEE-754 Float to int

[Greg KH]

On Tue, Nov 22, 2016 at 04:44:43PM +0000, Lucas Tanure wrote:
> 
> 
> On Tue, Nov 22, 2016 at 4:39 PM, Greg KH <greg@kroah.com> wrote:
> 
>     On Tue, Nov 22, 2016 at 04:05:18PM +0000, Lucas Tanure wrote:
>     > Hi,?
>     >
>     > At some point my hardware gives me a 32bit?IEEE-754 float, like this :
>     >
>     >
>     > regmap_read(device->regmap, ADDR0, &temp);
>     >
>     > value = temp << 16;
>     >
>     > regmap_read(device->regmap,?ADDR1, &temp);
>     >
>     > value |= temp;
>     >
>     >
>     > So, value has a 32bit float now, and I would like to print just the
>     integer
>     > part, like :
>     > Read 26.92387 --> Print 26.?
>     > Simple, no float operations.?
>     >
>     > How I can do it ?
> 
>     Just print the upper 16 bits shifted right by 16 bits.?
> 
> 
>     But why would you want to print the value anyway?? Who would use it?
> 
> My hardware gives me the board temperature as a float 32bits.?
> And the hwmon sysfs api asks me to return the temperature as?millidegree
> Celsius.
> 
> To follow the hwmon sysfs api rules, I need to get my float, multiply by 1000
> and print the integer part.?
> There is a better way to do that ?

Ah, yeah, sorry, my example is wrong.  There's got to be other drivers
that also do this same thing, try asking on the hwmon mailing list, they
should know how to do this best, as they are the ones responsible for
that user/kernel api.

thanks,

greg k-h

IEEE-754 Float to int

[Lucas Tanure]

On Tue, Nov 22, 2016 at 4:55 PM, Greg KH <greg@kroah.com> wrote:
> On Tue, Nov 22, 2016 at 04:44:43PM +0000, Lucas Tanure wrote:
>>
>>
>> On Tue, Nov 22, 2016 at 4:39 PM, Greg KH <greg@kroah.com> wrote:
>>
>>     On Tue, Nov 22, 2016 at 04:05:18PM +0000, Lucas Tanure wrote:
>>     > Hi,
>>     >
>>     > At some point my hardware gives me a 32bit IEEE-754 float, like this :
>>     >
>>     >
>>     > regmap_read(device->regmap, ADDR0, &temp);
>>     >
>>     > value = temp << 16;
>>     >
>>     > regmap_read(device->regmap, ADDR1, &temp);
>>     >
>>     > value |= temp;
>>     >
>>     >
>>     > So, value has a 32bit float now, and I would like to print just the
>>     integer
>>     > part, like :
>>     > Read 26.92387 --> Print 26.
>>     > Simple, no float operations.
>>     >
>>     > How I can do it ?
>>
>>     Just print the upper 16 bits shifted right by 16 bits.
>>
>>
>>     But why would you want to print the value anyway?  Who would use it?
>>
>> My hardware gives me the board temperature as a float 32bits.
>> And the hwmon sysfs api asks me to return the temperature as millidegree
>> Celsius.
>>
>> To follow the hwmon sysfs api rules, I need to get my float, multiply by 1000
>> and print the integer part.
>> There is a better way to do that ?
>
> Ah, yeah, sorry, my example is wrong.  There's got to be other drivers
> that also do this same thing, try asking on the hwmon mailing list, they
> should know how to do this best, as they are the ones responsible for
> that user/kernel api.
>
> thanks,
>
> greg k-h

Hi,

For future reference:

The best way to do it seems to be to write conversion function.
Receive the float in a u32, parse it's bits and return a s32. Can be
done without the use of floats.

Thanks!

-- 
Lucas Tanure

IEEE-754 Float to int

[Anupam Kapoor]

On Wed, Nov 23, 2016 at 6:00 PM, Lucas Tanure <tanure@linux.com> wrote:

> The best way to do it seems to be to write conversion function.
> Receive the float in a u32, parse it's bits and return a s32. Can be
> done without the use of floats.
>

?but this conversion-function might not be straight-forward :) ?it _may_ be
possibly simplified depending on your precision requirements etc. etc.

?--
kind regards
anupam?


In the beginning was the lambda, and the lambda was with Emacs, and Emacs
was the lambda.
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